Nongenetic factors associated with stress urinary incontinence.

OBJECTIVE:To explore the role of hereditary and environmental factors on the development of stress urinary incontinence in a large cohort of identical and nonidentical twins. METHODS:This is a large, population-based, classic twin study of twin sisters recruited to complete a health survey at the world's largest annual twins festival during 2003-2008. Concordance rates were calculated and structural equation models were used to estimate the contribution of genetic effects compared with environmental factors toward the development of stress urinary incontinence. RESULTS:Eight hundred eighty-two twin sister pairs (n=1,764), including 765 identical and 117 nonidentical twin sister pairs, completed the questionnaires. Sequential structural equation modeling revealed that common environmental factors contributed 77.6% (95% confidence interval [CI], 41.4-83.8; P<.001) of the variance and unique environmental factors contributed 20.9% (95% CI, 15.8-26.7; P<.001) of the variance. The effect of genetics was not statistically significant at 1.49% (95% CI, 0.0-38.8; P=.46). CONCLUSION:Female stress urinary incontinence is more a consequence of environmental risk factors than heredity. This epidemiologic insight should be considered in preventive health efforts. LEVEL OF EVIDENCE:II.